Black Holeballs are celestial bodies that eat whatever they can, even light. Some say that passing through causes time travel, or it leads to a Parallel Universeball, or simply everything it eats is compressed to a tiny ball - but nobody knows. If the Big Fire theory is true, he will be the only one left, if you don't count Dark Energy. Nobody knows how many of them there are (Its estimated to be Quadrillions around the Observable Universe). When a starball large enough blows up, sometimes they become one in a supernova explosion.
There are even supermassive black holes, these black holes can be only found if you go to the center of a galaxy. They are formed when many black holes merge together.
Now some people questioned their existence, or whether they existed at all. But in April 2019, the first picture ever was taken, one of the biggest achievements in space history.
There is a accretion disk which has a jet through it. The jet contains atomic matter .On the top and bottom of the accretion disk is a corona. The corona contains hot electrons. In the middle there is a black hole through it.
Massive stars, upon death expand until they are red supergiants. Then they explode. The explosion is called a supernova. Then the stars have a chance to become black holes or neutron stars.
Black holes slowly loose there particles, which is called hawking radiation. More massive black holes do this slower. Smaller black holes emit hawkings radiation faster. The process can take to uncountable years.
Sagittarius A*ball is a bright black hole in the center of the Milky Wayball. It was discovered in 1974.